The Federal Communication Commission (FCC) proposed in the mid-1990's the establishment of the Emergency Alert System (EAS) as a replacement for the aging Emergency Broadcast System (EBS). The creation of the EAS has allowed for and continues to improve the dissemination of information vital to ensuring the safety of the public in the event of severe weather, catastrophic event and/or terrorist attacks. The EAS system has adopted a mandatory standard digital protocol that will be used by all broadcast station licensees, including noncommercial educational class D FM stations and low power TV stations. The creation of this universal digital protocol would now make it possible to develop universal paging systems for any part of the country served by the EAS network. The Purple Tree Technologies proposed system would consist of a methodology for acquiring the EAS signal from originator of the message such as Emergency Action Notification Network (EAN), Primary Entry Point System (PEP), the National Weather Service (WXR), the civil authorities (CIV), or a broadcast station or cable system (EAS), developed to activate the cell towers and/or satellites in the area affected by the event, and the device designed with today's technology to be similar in size of a key chain remote for keyless entry system used in automobiles around the world.
Emergency Alert System consists of a network of encoders and decoders located at all broadcast stations nation wide for the purpose of notifying the public of national emergencies. This system is also being used by state and local emergency management personnel for warning the public of pending severe weather, tornados, radioactive release, Amber alerts, etc. The FCC has adopted a mandatory protocol for the transmission of signals which includes state and local identification and emergency codes. This universal approach greatly enhances our ability to adopt a national approach in creating a personal portable emergency alert system. The Federal Communication Commission released the details, including location and emergency codes, of the proposed Emergency Alert System in document FCC 94-288.
Once an EAS signal has been encoded and transmitted, the National Oceanic and Atmospheric Administration (NOAA) will have access to the information that not only includes weather-related events but also other catastrophic events, Amber alerts and/or terrorist attacks, for example. The ability to access NOAA's database with regards to the EAS transmitted code would allow for the identification of the location of the warning area and the type of emergency just as hundreds of broadcast stations are notified hundreds of times a year—without the cost of tapping into EAS units throughout the country. Federal, state, or local governmental agencies requiring the ability to transmit emergency broadcast to populace would have same capability with similar set-up.
When mobile phones were first developed, their purpose was simply to allow for voice communications. Most of these systems used analog technologies that transmitted voice over a finite number of FM radio bands. These systems are all but non-existent today and are known as first generation (1G) cellular networks. The second generation (2G) networks began to emerge in the 80's as digital networks. These continued to focus on voice communication, but added some extended features such as basic text or email messaging, caller id, multi-way calling, extended roaming, and the ability to handle more users.
There were two competing underlying technologies for 2G networks developed that are worth mentioning. The first of these is time division multiple access (TDMA). This approach to sending digital signals through the air divides the allocated cell bandwidth (there are two major bands allocated by the FCC to cell phones: 824-894 Mhz and 1850-1990 Mhz) into a series of narrow bands. These narrow bands are then divided into multiple time slices. Each time slice with in a band constitutes a communication channel with a given mobile device. The major networking technologies that use this method are GSM and IS-136. Though there are many other TDMA networking standards, these are the only two with any significant land coverage.
The other 2G technology developed is code division multiple access (CDMA). This technology allows transmission of data over the entire allotted cellular phone spectrum. The messages for a specific mobile device will be coded with a unique signature that the device can recognize and interpolate from the broadband data stream. This technology is similar to a large party where everyone is speaking at once, but one can differentiate conversation either by voice or by language. Because the entire spectrum is used, and individual bands or time slices do not need to be allocated, higher data rates can be achieved. Also, an additional advantage is the “soft” user limit. There is not a finite number of channels available for subscribers, instead, as the number of users on a given cell increases, the available bandwidth per user decreases. The result is added noise or slower connections as traffic increases rather than denial of service. The primary 2G networking standard adopted on CDMA is commonly referred to as cdmaOne. This includes the IS-95-A and IS-95-B standards.
Recently, the rapid expansion of the Internet and increased demand for mobile data services has led to the development of third generation (3G) networks. The primary impetus for 3G networks is to allow for internet protocol (IP) connection and functionality for mobile devices. These networking standards are extremely complex and any functional description of them is beyond the scope of this paper. However, they have many features that are very relevant to the development of an emergency broadcast system. Because of the high data rates required by most IP based services CDMA is the radio interface of choice for 3G networks. The most common networking protocols that fall in this category are CDMA2000-1x and WCDMA, also known as UMTS. UMTS is considered to be the ultimate goal for 3G technology.
There is another protocol worth mentioning that does not fall directly into either 2G or 3G category. GPRS is an addendum to the GSM networking standard that implements an “always on” IP connection to the internet. Because this is not a fully realized 3G standard, but goes beyond standard 2G services, GPRS is often referred to as being 2.5G. GPRS is currently implemented in most GSM networks world wide. Also, more recently EDGE technology has been developed as an enhancement to GPRS services, though it is not as widely implemented.
Today, most cellular network providers are in a long process of upgrading from 2G networks to 3G networks. AT&T® and Cingular®, two of the largest owners of IS-136 networks are on a migration path to GSM networking technology and then eventually to UMTS. Though UMTS realization on these networks probably will not for several years, they have already deployed GSM/GPRS networks across most major population centers in the U.S. Other companies, such as Verizon®, currently have functioning cdmaOne networks covering most of the U.S. land area and are in the process of upgrading to CDMA2000-1x and eventually to UMTS. Other cellular companies are at different stages in development but still evolving towards UMTS.
In order to broadcast from a cellular network to all devices in the cell, the format of the data must be such that it does not disrupt other communications over the network. This means that any technology chosen must already be designed for cell broadcast functions. The networking technologies that are designed to do this kind of broadcasting are the 2.5G and 3G networks. The specific technologies that support cell broadcasting are GPS/GPRS/EDGE, CDMA2000-1x, and UMTS. GPS networks implement the cell broadcasts through GPRS/EDGE service enhancements. These enhancements allow short, unacknowledged, text messages to be transmitted to all or a group of mobile devices within a cell. The mobile devices may be configured to receive all broadcasts or just specific kinds of broadcasts depending on the user's preferences. UMTS networks also support the GPRS/EDGE broadcast controls in addition to other more powerful native broadcast controls. Some of the more powerful controls allow for broadcast audio, images, and even video. Though CDMA2000-1x networks are not natively capable of broadcast messages, discussion of implementing the GPRS text broadcasting controls on these networks has reached public forums in late 2003 and early 2004. The date of implementation for these services is not clear.
There are three factors to consider when choosing a networking standard for the inexpensive alert receivers. One is the coverage area of existing networks. Currently GSM/GPRS covers most population centers in the U.S. CDMA2000-1x is rapidly expanding and may soon cover more area than GSM. UMTS technology is not as widely available in the U.S. The second consideration is reliability of the technology. GSM/GPRS has been time tested in Europe and other parts of the world for over a decade. The CDMA based networks are all relatively young. The third consideration is cost. This must also take into account maintenance costs. GSM technology, because of its world wide use, is probably the cheapest to implement. However, CDMA technologies, especially UMTS, are likely to be supported for the longest time and would not need to be replaced as soon.